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- Beckmann, K., et al.
(författare)
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Formation of stoichiometrically O-18-labelled oxygen from the oxidation of O-18-enriched water mediated by a dinuclear manganese complex : a mass spectrometry and EPR study
- 2008
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 1:6, s. 668-676
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen formation was detected for the oxidations of various multinuclear manganese complexes by oxone (HSO5-) in aqueous solution. To determine to what extent water was the source of the evolved O-2, (H2O)-O-18 isotope-labelling experiments coupled with membrane inlet mass spectrometry (MIMS) were carried out. We discovered that during the reaction of oxone with [Mn-2(OAc)(2)(bpmp)](+) (1), stoichiometrically labelled oxygen (O-18(2)) was formed. This is the first example of a homogeneous reaction mediated by a synthetic manganese complex where the addition of a strong chemical oxidant yields O-18(2) with labelling percentages matching the theoretically expected values for the case of both O-atoms originating from water. Experiments using lead acetate as an alternative oxidant supported this finding. A detailed investigation of the reaction by EPR spectroscopy, MIMS and Clark-type oxygen detection enabled us to propose potential reaction pathways.
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- Hammarström, Leif, et al.
(författare)
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Proton-coupled electron transfer of tyrosines in Photosystem II and model systems for artificial photosynthesis : the role of a redox-active link between catalyst and photosensitizer
- 2011
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 4:7, s. 2379-2388
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Tidskriftsartikel (refereegranskat)abstract
- Water oxidation in Photosystem II is dependent on a particular amino acid residue, Tyrosine(Z). This is a redox intermediate in steady state oxygen evolution and transfers electrons from the water splitting CaMn4 cluster to the central chlorophyll radical P-680(+). This Perspective discusses the functional principles of Tyrosine(Z) as a proton-coupled redox active link, as well as mechanistic studies of synthetic model systems and implications for artificial photosynthesis. Experimental studies of temperature dependence and kinetic isotope effects are important tools to understand these reactions. We emphasize the importance of proton transfer distance and hydrogen bond dynamics that are responsible for variation in the rate of PCET by several orders of magnitude. The mechanistic principles discussed and their functional significance are not limited to tyrosine and biological systems, but are important to take into account when constructing artificial photosynthetic systems. Of particular importance is the role of proton transfer management in water splitting and solar fuel catalysis.
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- Koroidov, Sergey, et al.
(författare)
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First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles
- 2015
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 8:8, s. 2492-2503
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Tidskriftsartikel (refereegranskat)abstract
- Co-oxides are promising water oxidation catalysts for artificial photosynthesis devices. Presently, several different proposals exist for how they catalyze O2 formation from water. Knowledge about this process at molecular detail will be required for their further improvement. Here we present time-resolved 18O-labelling isotope-ratio membrane-inlet mass spectrometry (MIMS) experiments to study the mechanism of water oxidation in Co/methylenediphosphonate (Co/M2P) oxide nanoparticles using [Ru(bpy)3]3+ (bpy = 2,2'-bipyridine) as chemical oxidant. We show that 16O–Co/M2P-oxide nanoparticles produce 16O2 during their first turnover after simultaneous addition of H218O and [Ru(bpy)3]3+, while sequential addition with a delay of 3 s yields oxygen reflecting bulk water 18O-enrichment. This result is interpreted to show that the O–O bond formation in Co/M2P-oxide nanoparticles occurs via intramolecular oxygen coupling between two terminal Co–OHn ligands that are readily exchangeable with bulk water in the resting state of the catalyst. Importantly, our data allow the determination of the number of catalytic sites within this amorphous nanoparticular material, to calculate the TOF per catalytic site and to derive the number of holes needed for the production of the first O2 molecule per catalytic site. We propose that the mechanism of O–O bond formation during bulk catalysis in amorphous Co-oxides may differ from that taking place at the surface of crystalline materials.
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- Shevchenko, Denys, et al.
(författare)
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Photochemical water oxidation with visible light using a cobalt containing catalyst
- 2011
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Ingår i: Energy and Environmental Science. - : RSC Publishing. - 1754-5692 .- 1754-5706. ; 4:4, s. 1284-1287
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Tidskriftsartikel (refereegranskat)abstract
- Artificial photosynthesis aims at using solar light energy to oxidatively split water to oxygen, protons and electrons and store the energy in a chemical fuel. Here we present a cobalt phosphonate material that can split water catalytically, driven by visible light in aqueous solutions of pH 7.
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